1. Field of the Invention
The invention relates to sealing for conduits, cables and conductors, more specifically to a plug for passing conduits, cables and the like with enlarged terminations, through an opening in a pressure wall, and providing a pressure seal for the conduits and cables within the wall opening without having to remove the terminations.
2. Description of the Prior Art
It often becomes necessary to temporarily connect a wire, cable, or fluid conduit, which terminates in a connector of larger diameter than the wire, cable or conduit, from an apparatus outside a pressure vessel to a receptacle on an item that is within the pressure vessel without interfering with the primary seal to the vessel.
One way that this is done is by including a plurality of pressure resistant through-connectors and terminations of various sizes and types permanently mounted in a vessel wall seal plate in anticipation of their need. The lines are then connected at the plate on the outside of the vessel by their plugs to mating receptacles or are modified for that purpose (e.g. stripped and soldered) and connected, while another set of lines and plugs are connected to their mates on the plate at the inside of the vessel and connected to the item.
This method limits the number and variety of lines and often requires that they be reworked to obtain suitable termination. Cost, delay and reduced reliability are incurred.
Another way employs a non-porous foam, formed around the wires, cables or fluid conduits, contained by an opening in the vessel wall. This method requires a long curing process for the foam, and does not provide a verifiable seal. The seal is also fragile, and susceptible to performance degradation.
The sealing art for conduits, cables and conductors is also replete with plugs of various designs. For example, M. B. Mallett et al., in U.S. Pat. No. 3,314,030, patented Apr. 11, 1967, discloses a tubular shell that is sealingly welded at one end in an opening in the wall of a high voltage oil filled transformer. The other end of the shell is outside-threaded to receive an inside-threaded cap that is made from an electrical insulative material.
Axially stacked within the shell, are three insulators in order, a hard washer, a resilient grommet, and a hard washer. An opening for a high voltage cable runs axially through the cap, washers, grommet and shell. The opening is of sufficient diameter to receive a stiff insulating sleeve that surrounds the copper wire of the cable. The insulating cover of the cable is cut back so that a portion of the end is received in an expanded annular recess at one end of the insulating sleeve. A minor diameter portion of the cap extends over that end of the insulating sleeve for protection against electrical tracking or surface arcing.
The cable, preferably of uniform diameter, is installed in the plug by pushing it in from one end.
When the cap is screwed down on the shell, it engages an optional intermediate element which in turn axially compresses the washer and grommet assembly against a shell wall. This causes the grommet to expand radially against the insulating sleeve and the shell wall.
As the grommet material is relatively incompressible, a series of annular peripheral grooves are provided, which have a volume equal to or greater than the volume loss of cable insulation under extreme cable deformation. This assures that a spring action is provided within the grommet so that a sealing grip on the cable is maintained.
In another embodiment in which a plurality of wires pass through the plug, each in a hole through the grommet, the spring action is helped by provision of several axial bores in the grommet, on a constant radius, which crush upon lock down pressure, instead of the annular peripheral grooves.
In U.S. Pat. No. 4,267,401, patented May 12, 1981 by W. L. Wilkinson, a pressure plug for a plurality of conductors is described. In the plug, a resilient seal disk includes a plurality of axial openings through the disk, located on a constant radius. Each opening has an axial slit across its outer wall which radially opens the hole to the outer diameter of the disk.
The disk is located between a pair of parallel pressure plates having holes which line up with the openings in the seal disk.
A central axial bore passes through the disk and plate stack for receiving a threaded bolt.
In installation of the plug and wire in a pressure wall, an un-terminated wire or a sealing pin with round head at its back, is pushed through each set of aligned holes from one end of the stack. The bolt is then tightened so that the plates squeeze the seal. The axially compressed seal consequently expands radially, sealing against the surrounding wall of the opening in the pressure vessel wall. It also presses against the through-wire and pins to establish a pressure seal for the contained wires as they pass through the pressure wall.
In an embodiment for installing cables without removing connectors from the cable ends, each hole in the plates is keyhole shaped, with the base of the keyhole opening radially to the outer edge of the plate. Instead of pushing the wire or pin through the stack from one end, the wire or pin is slipped sideways into the keyhole in the plate, and through the slit in the seal disk into the corresponding seal disk hole. The bolt is then tightened as above.
One problem in the above design is that a balance must be struck between the width of the keyhole base opening to accommodate the diameter of the wire with respect to the hole in which it will reside, and the axial pressure area of the plate that is sacrificed due to the width of the keyhole base opening.
Even for the thinnest of wires for which only a narrow plate opening is needed, the keyhole base opening in the plate remains to be a site of reduced axial pressure near the seal disk periphery.
Reduced axial pressure area for bearing on the seal disk results in reduced radial pressure for sealing of the disk material inwardly against the wire, outwardly against the inner face of the pressure wall, and at the radial slit in the seal.
It is one object of the present invention to provide a penetration plug for sealing installation of wire or conduit having a termination, through a pressure wall opening without having to remove the termination.
It is another object to provide the above penetration plug for sealing installation of wire which will receive wire up to the maximum diameter of the hole through the plug, without sacrifice of axial pressure which effects sealing quality.
It is another object to provide a penetration plug with means for monitoring the seal for leakage.
Additional objects and advantages will become apparent from the ensuing description of the invention.
In accordance with the invention, a first resilient wall includes a first opening through the outer diameter of the first wall, for a line through the first wall. A second wall that is stiffer than the first wall forms a second opening for traversing of the second wall by the line. The outer diameter of a third wall that is stiffer than the first wall is unbroken, approximately the same radial size as the resilient first wall, and forms a third opening for receiving a insert. The first wall is squeezed between the second wall and the third wall plus insert by a first means for squeezing, for displacing material of the first wall against the line and against an inner wall of a hole in which the plug is mounted.
A seat in the third wall is shaped for slidingly unencumbered axial movement of the insert from introduction into the seat to a fully seated position in the third wall.
The third wall and first insert form between them an opening for passing the line between them when the insert is seated in the third wall.
One of the third wall and insert is adapted for transferring a portion of squeezing force from the first squeezing means for squeezing to the other of the third wall and insert, for the squeezing of the first wall by the third wall and insert.
A second means for squeezing a fourth resilient wall for displacing the fourth wall against the inner wall of the hole in which the plug is mounted, may comprise a fifth wall with a boss.
The second means for squeezing is operated by the first means for squeezing. The fifth wall and boss contribute to spacing the fourth wall from the second wall for forming a sealed cavity between the resilient first and fourth walls and the inner wall.